Implants including spacers for use in brachytherapy and other radiation therapy that resist migration and rotation

ABSTRACT

A brachytherapy implant includes a plurality of protrusions to reduce a tendency of the implant to migrate and rotate within a patient&#39;s body after implantation. Embodiments of the present invention are directed to spacers that resist migration and rotation. This abstract is not intended to be a complete description of the invention.

CLAIM TO PRIORITY

This application is a continuation of U.S. patent application Ser. No.11/187,411, filed Jul. 22, 2005, entitled “Implants for use inBrachytherapy and Other Radiation Therapy That Resist Migration andRotation,” which is incorporated herein in its entirety.

FIELD OF THE INVENTION

This invention relates to radiotherapy. More particularly, it relates toimplants for use in brachytherapy, and in particular to therapeuticmembers, spacers and strands that are used to resist migration androtation of radioactive sources. The invention also relates toimplantable radiopaque markers that resist migration and rotation.

BACKGROUND

Brachytherapy is a general term covering medical treatment whichinvolves placement of radioactive sources near a diseased tissue and mayinvolve the temporary or permanent implantation or insertion ofradioactive sources into the body of a patient. The radioactive sourcesare thereby located in proximity to the area of the body which is beingtreated. This has the advantage that a high dose of radiation may bedelivered to the treatment site with relatively low doses of radiationto surrounding or intervening healthy tissue. Exemplary radioactivesources include radioactive seeds, radioactive rods and radioactivecoils.

Brachytherapy has been used or proposed for use in the treatment of avariety of conditions, including arthritis and cancer. Exemplary cancersthat may be treated using brachytherapy include breast, brain, liver andovarian cancer and especially prostate cancer in men. For a specificexample, treatment for prostate cancer may involve the temporaryimplantation of radioactive sources (e.g., rods) for a calculatedperiod, followed by their subsequent removal. Alternatively, theradioactive sources (e.g., seeds) may be permanently implanted in thepatient and left to decay to an inert state over a predictable time. Theuse of temporary or permanent implantation depends on the isotopeselected and the duration and intensity of treatment required.

Permanent implants for prostate treatment include radioisotopes withrelatively short half lives and lower energies relative to temporaryseeds. Exemplary permanently implantable sources include iodine-125,palladium-103 or cesium-131 as the radioisotope. The radioisotope can beencapsulated in a biocompatible casing (e.g., a titanium casing) to forma “seed” which is then implanted. Temporary implants for the treatmentof prostate cancer may involve iridium-192 as the radioisotope. Fortemporary implants, radioactive rods are often used.

Conventional radioactive seeds are typically smooth sealed containers orcapsules of a biocompatible material, e.g., titanium or stainless steel,containing a radioisotope within the sealed chamber that permitsradiation to exit through the container/chamber walls. Other types ofimplantable radioactive sources for use in radiotherapy are radioactiverods and radioactive coils, as mentioned above.

Preferably, the implantation of radioactive sources for brachytherapy iscarried out using minimally-invasive techniques such as, e.g.,techniques involving needles and/or catheters. It is possible tocalculate a desired location for each radioactive source which will givethe desired radiation dose profile. This can be done using knowledge ofthe radioisotope content of each source, the dimensions of the source,accurate knowledge of the dimensions of the tissue or tissues inrelation to which the source is to be placed, plus knowledge of theposition of the tissue relative to a reference point. The dimensions oftissues and organs within the body for use in such dosage calculationsmay be obtained prior to or during placement of the radioactive sourcesby using conventional diagnostic imaging techniques including X-rayimaging, magnetic resonance imaging (MRI), computed tomography (CT)imaging, fluoroscopy and ultrasound imaging.

During the placement of the radioactive sources into position, a surgeoncan monitor the position of tissues such as the prostate gland using,e.g., ultrasound imaging or fluoroscopy techniques which offer theadvantage of low risk and convenience to both patient and surgeon. Thesurgeon can also monitor the position of the relatively large needleused in implantation procedures using ultrasound or other imaging.

Once implanted, radioactive sources (e.g., seeds, rods or coils) areintended to remain at the site of implantation. However, the radioactivesources may on some occasions migrate within a patient's body away fromthe initial site of implantation. This is undesirable from a clinicalperspective, as migration may lead to underdosing of a tumor or otherdiseased tissue and/or exposure of healthy tissue to radiation.Additionally, there have been reported incidents where a migrated seedimplant has caused a pulmonary embolism. Accordingly, there is a need toreduce the tendency for radioactive sources to migrate within apatient's body.

Radioactive sources may also on some occasions rotate or twist from theoriginal orientation at which the seed was implanted. This is alsoundesirable from a clinical perspective, because the radiation patternof the sources may be directional, thereby causing underdosing oroverdosing of a tumor or other diseased tissue and/or exposure ofhealthy tissue to radiation. Accordingly, there is also a need to reducethe tendency for radioactive sources to rotate within a patient's body.

Efforts have been made to reduce the tendency for radioactive seeds tomigrate within a patient's body. For example, U.S. Pat. No. 6,632,176(the '176 patent) discloses a radioactive seed having a biocompatiblecontainer with at least one part of a surface of the container beingroughened, shaped or otherwise treated so that it is no longer smooth.According to the '176 patent, the roughening, shaping or other treatmentis achieved by: forcing the seed container through a ridged or serrateddye or a threading device to impart grooves on the outer surface of thecontainer; milling the seed container; using a wire brush, file, orsandpaper to roughen the outer surface of the container; etching using alaser or water jet cutter, or by electrolytic etching; blasting (e.g.,sand blasting); or electroplating.

Disadvantages of the radioactive seeds disclosed in the '176 patent isthat they are not off the shelf seeds, but rather, are custom seedswhose manufacturing cost is likely higher than that of a typicalradioactive seed. Additionally, even though the '176 patent says thatthe treatment process should not compromise the integrity of thecontainer, the integrity of the container may indeed be affected by theroughing, shaping and other treatments suggested in the '176 patent.Additionally, because the containers themselves are being changed, theradioactive seeds having such roughened, shaped or otherwise treatedcontainers may be subject to government certification orre-certification. Further, the modified containers may affect thedirectional radiation pattern of the seed, potentially resulting inadverse clinical results. Accordingly, it is preferred that the means ofreducing the tendency for radioactive seeds to migrate and/or rotatewithin a patient's body overcome the above mentioned disadvantages.

When performing external beam radiation procedures such as intensitymodulated radiation therapy (IMRT) and conformal radiation therapy (CRT)it is important that a target for radiation be accurately identified. Toaccomplish this, radiopaque markers (sometime referred to as fiducial orfiduciary markers) are often implanted into the patient at or near thetarget, so that the radiation can be accurately focused. Once implanted,such markers are intended to remain at the site of implantation.However, the markers may on some occasions migrate and/or rotate withina patient's body away from the initial site of implantation. This isundesirable because it is the locations of the markers that are used todetermine where to focus the radiation treatments. Accordingly, there isa need to reduce the tendency for such markers to migrate and/or rotatewithin a patient's body.

SUMMARY OF THE INVENTION

Embodiments of the present invention are directed to therapeutic membersand strands for use in brachytherapy. Such members and strands, as willbe understood from the detailed description, are designed to reduce thetendency for the members and strands (and thus the radioactive sourcestherein) to migrate and/or rotate within a patient's body.

In one embodiment a member includes a radioactive source and a materialthat encapsulates the radioactive source. Such encapsulating material,which is preferably, but not necessarily, bio-absorbable, is likelypolymeric or some other plastic material. An outer surface of theencapsulating material includes at least one protrusion, and preferablya plurality of protrusions, to reduce the tendency of the member tomigrate and rotate within a patient's body after implantation.

In accordance with an embodiment, one or more of the protrusions extendin a radial direction (e.g., perpendicular or at an acute angle) withrespect to a longitudinal axis of the radioactive source. One or moreprotrusions may also extend in a longitudinal direction with respect tothe radioactive source. Such protrusions can have various shapes, suchas, but not limited to, square, rectangular, circular, oval, triangular,pyramidal and semi-spherical, or combinations thereof.

In accordance with an embodiment, the one or more protrusions includeone or more ribs that form one or more rings or a helix about a radialcircumference of the radioactive source.

In accordance with another embodiment, the plurality of protrusionsforms an irregular pattern on the outer surface of the encapsulatingpolymeric material. For example, the plurality of protrusions can form asurface that resembles a rough stucco surface.

In another embodiment, the encapsulating material is used to form ananchor mechanism that extends from at least one of the longitudinal endsof the radioactive seed to reduce a tendency of the member to migrateand rotate within a patient's body after implantation. In accordancewith an embodiment, a void is formed between the anchor mechanism andthe portion of the material that encapsulates the radioactive source, toallow patient tissue to enter the void after implantation.

Embodiments of the present invention are also directed to spacers, whichare used to separate radioactive sources from one another, wherein thespacers include protrusions and/or anchor mechanisms, similar to thosedescribed above.

Embodiments of the present invention are also directed to strands thatinclude protrusions and/or anchor mechanisms, similar to those describedabove. Such strands include a plurality of radioactive sources that arespaced apart from one another at desired intervals.

Embodiments of the present invention are also directed to spacers andstrands that include portions that are biased to open afterimplantation, to thereby engage surrounding tissue.

Embodiments of the present invention are also directed to radiopaquemarkers that include protrusions and/or anchor mechanisms, similar tothose described above, to reduce the tendency of the markers to migrateand rotate within a patient's body after implantation.

Embodiments of the present invention are also directed to an anchormechanism that includes a sleeve to fit around a structure, such as aradioactive source, a thermal ablation implant, a spacer, a strand or aradiopaque marker. One or more wing is connected to the sleeve by acorresponding living hinge that enables the wing to be folded againstthe structure during implantation of the structure in a patient. Theliving hinge biases the wing such that one end of the wing moves awayfrom the structure to engage surrounding patient tissue afterimplantation of the structure into a patient. This engagement of thewing with the tissue reduces a tendency for the structure to migrate androtate after implantation.

This summary is not intended to be a complete description of theinvention. Other features, aspects, objects and advantages of theinvention can be obtained from a review of the specification, thefigures, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a side view of a therapeutic member according to anembodiment of the present invention; and FIG. 1B is a perspective viewof the therapeutic member shown in FIG. 1A.

FIGS. 2-5 are side views of therapeutic members according to variousembodiments of the present invention.

FIG. 6A is a side view of a therapeutic member according to a furtherembodiment of the present invention; and FIG. 6B is a perspective viewof the therapeutic member shown in FIG. 6A.

FIG. 7A is a side view of a therapeutic member according to anotherembodiment of the present invention; and FIG. 7B is a perspective viewof the therapeutic member shown in FIG. 7A.

FIG. 8A is a side view of a member with tabs; FIG. 8B is a perspectiveview of the member shown in FIG. 8A; FIG. 8C is a side view of thetherapeutic member of FIGS. 8A and 8B after the tabs have been shapedinto anchor mechanisms; FIG. 8D is a perspective view of the membershown in FIG. 8C; and FIG. 8E is an end view of the therapeutic membershown in FIGS. 8C and 8D.

FIG. 9 is a side view of an exemplary applicator that can be used toimplant therapeutic members of the present invention into a patient'sbody.

FIG. 10A is a perspective view of a spacer according to an embodiment ofthe present invention, in an open position; FIG. 10B is a perspectiveview of the spacer in FIG. 10A in a closed position; and FIG. 10C is aperspective view of the spacer of FIGS. 10A and 10B in a partiallyopened position.

FIG. 11 is a side view of a strand according to an embodiment of thepresent invention.

FIG. 12 is a side view of a strand according to another embodiment ofthe present invention.

FIG. 13 is a perspective view of a strand that includes portions whichare biased to open after implantation, and thereby engage tissuesurrounding the strand, to prevent migration and rotation of the strand.

FIG. 14A is a side view illustrating an anchor mechanism according to anembodiment of the present invention, it its closed position; FIG. 14B isa perspective view of the anchor mechanism of FIG. 14A, in its closedposition; FIG. 14C is a side view of the anchor mechanism of FIGS. 14Aand 14B, in its open position; and FIG. 14D is a perspective view of theanchor mechanism of FIGS. 14 A-C, in its open position.

DETAILED DESCRIPTION

Embodiments of the present invention relate to therapeutic members foruse in treatments such as brachytherapy. As shown in FIGS. 1A and 1B,each member 100 includes a radioactive source 102 (shown in dashed line)and a material 104 that encapsulates the radioactive source 102. Theradioactive source 102 can be a radioactive seed, a radioactive rod, ora radioactive coil, but is not limited thereto. The material 104 ispreferably, but not necessarily, bio-absorbable. In accordance with anembodiment, the material 104 is also bio-adherent. Additionally, thematerial 104 is preferably a polymeric material or some other plastic.Also shown in FIG. 1 is that an outer surface of the encapsulatingmaterial 104 includes protrusions 106 to reduce a tendency of the member100 to migrate and rotate within a patient's body after implantation.Also shown in FIG. 1B (in dotted line) is a longitudinal axis of theradioactive source 102, which is also the longitudinal axis of thetherapeutic member 100. The overall shape of the therapeutic member 100,excluding the protrusions 106, can be cylindrical with flat ends 120 and122, cylindrical with rounded (e.g., bullet shaped) ends 120 and 122 orrectangular, but is not limited thereto.

The protrusions that are used to reduce a tendency of the member tomigrate and rotate can be of any number of different shapes and sizes,or combinations thereof. For example, in FIGS. 1A and 1B the protrusions106 are shown as being square or rectangular knobs that cause the outersurface of the therapeutic member 100 to resemble a knobby tire. Theprotrusions 106 can form a plurality of rows (e.g., four rows) which areregularly spaced about the member 100, e.g., with each row extending ina direction that is 90 degrees from the adjacent rows. Alternatively,the protrusions can protrude in a more random or irregular fashion.

Exemplary dimensions for one of the protrusions 106 in FIG. 1B is shownas being 0.010×0.008×0.003 inches. All of the protrusions 106 can havesimilar dimensions, or the dimensions of the protrusions may vary. Forexample, it is possible that the protrusions within a row have similardimensions, but the dimensions differ for different rows. For a morespecific example, another row of protrusions 106 have dimensions of0.006×0.005×0.002 inches. These are just a few examples. One of ordinaryskill in the art will appreciate from this description that theprotrusions can have other dimensions while being within the scope ofthe present invention.

Preferably, the protrusions extend at least 0.002 inches so that theycan sufficiently grip into patient tissue (analogous to a knobby tiregripping soft dirt). The protrusions 106 can extend radially from thetherapeutic member 100. For example, in the embodiments shown, theprotrusions 106 extend in directions that are generally perpendicular tothe longitudinal axis 103 of the therapeutic member 100 and the source(e.g., seed) 102 therein. The protrusions 106 may alternatively oradditionally extend at other angles with respect to the longitudinalaxis 103. For example, protrusions may extend at 45 degrees with respectto the longitudinal axis 103. In a specific embodiment, each half of themember 100 can have protrusions 106 at a 45 degree angle facing towardsthe middle of the member 100, or towards the ends of the member 100.Various other angles, and combinations of angles, are also possible.

FIGS. 1A and 1B, and FIGS. 2-5 discussed below, the protrusions areshown as extending from the length of the therapeutic member. However,the protrusions may also extend from the longitudinal ends of thetherapeutic member.

In another embodiment, shown in FIG. 2, the protrusions 206 of atherapeutic member 200 are cylindrical. In still another embodiment,shown in FIG. 3, a therapeutic member 300 includes protrusions 306 thatresemble bumps or semi-spheres. In the embodiment shown in FIG. 4 theprotrusions 406 of a therapeutic member 400 are triangular, and in theembodiment of FIG. 5 the protrusions 506 of a therapeutic member 500 arepyramidal. These are just a few examples of the shapes of theprotrusions. One of ordinary skill in the art reading this descriptionwould appreciate that other shapes are also possible. It should also beunderstood that a therapeutic member of the present invention caninclude protrusions of numerous different shapes, including, but notlimited to, the shapes shown in FIGS. 1-5. While in the FIGS. thevarious protrusions are shown as having a common orientation, it is alsowithin the scope of the present invention that the protrusions havedifferent orientations. For example, in FIG. 5, different triangularprotrusions 506 can have different orientations.

In a further embodiment, shown in FIGS. 6A and 6B, the protrusions areribs 608 that encircle the underlying source 102. Four ribs 608 areshown in FIGS. 6A and 6B. However, it should be understood that more orless ribs 608 can be included. It should also be understood the ribs canbe helical (i.e., spiral). In one specific embodiment, the ribs can formcounter balancing screw threads (i.e., opposing helixes). For example,the threads on one half of the member can be right hand threads, whilethe threads on the other half of the member can be left hand threads.

In another embodiment, the plurality of protrusions can form anirregular pattern on the outer surface of the encapsulating polymericmaterial 104. For example, the protrusions can form what resembles arough stucco like surface, e.g., as shown in FIGS. 7A and 7B.

In the embodiments where the radioactive sources 102 are radioactiveseeds, the seeds 102 can be of various types having low energy and lowhalf-life such as Iodine seeds, known as I-125 seeds, including a weldedtitanium capsule containing iodine 125 adsorbed on a silver rod, orPalladium 103 seeds. Seeds may also have there isotope adsorbed onceramic beads, resin beads, silver beads, graphite pellets, porousceramic rods, copper cores, etc. Seed can have various different shapes,such as, but not limited to, cylindrical with flat ends, cylindricalwith rounded (e.g., bullet shaped) and spherical. Exemplary dimensionsof a seed 102 are 0.18 inches in length and 0.0315 inches in diameter.Exemplary seeds are listed below in Table 1, but embodiments of thepresent invention should not be limited to the seeds listed therein.

TABLE 1 Seed Manufacturers and Common Types of Seeds MANUFACTURER SEEDNAME IODINE¹²⁵ Amersham 6711 OncoSeed Amersham 6733 EchoSeed Amersham7000 RAPID Strand North American Scientific IoGold Best Industries BESTIodine-125 Bebig Symmetra Mills Biopharmaceuticals ProstaSeed SyncorPharmaSeed International Isotopes IsoStar Implant Sciences I-PlantInternational Brachytherapy InterSource-125 IsoAid Advantage I-125Source Tech STM1251 DRAXIMAGE, Inc. BrachySeed PALLADIUM¹⁰³ NorthAmerican Scientific Pd Gold Theragenics Theraseed 200 Best IndustriesBEST Palladium-103 International Brachytherapy InterSource 103

Alternatively, seeds 102 can be manufactured using iridium 192, cesium131, gold 198, yttrium 90 and/or phosphorus 32. Further radioactiveisotopes used to manufacture seeds are not limited to these examples,but can include other sources of different types of radiation.

In addition it is to be understood that other types of seeds can beused. For example, seeds such as those described in U.S. Pat. No.6,248,057, which is incorporated herein by reference, can be used withthe present invention. These seeds include radiation delivery devices,drug delivery devices, and combinations of radiation and drug deliverydevices in the form of beads, seeds, particles, rods, gels, and thelike. These particular seeds are absorbable wherein the radiation memberor drug delivery member is contained within, for example, absorbablepolymers such as those listed below or in the above-referenced patent.In such seeds, the bio-absorbable structure can have a predefinedpersistence which is the same as or substantially longer than a halflife of the radioactive member contained in the bio-absorbablestructure. These above bio-absorbable seeds can be used in the samemanner as the seeds described herein with respect to the invention. Asmentioned above, the radioactive sources 102 need not be seeds. Forexample, the radioactive sources 102 can be rods, e.g., metallic rodscoated with a radioactive isotope such as palladium 103, etc. Theradioactive sources 102 may also be radioactive coils, such as thosedescribed in U.S. Pat. No. 6,419,621, which is incorporated herein byreference, and those available from RadioMed Corporation of Tyngsboro,Mass., under the trademarks GENETRA and RADIO COIL. In accordance withan alternative embodiment, rather than using a radioactive source, animplant that utilizes thermal ablation to treat cancer can be used. Onesuch implant, which is marketed under the trademark ThremoRod, and isavailable from Ablation Technologies of San Diego, Calif., is apermanently implantable cobalt-palladium alloy rod that produces heat(e.g., 70° C.) through oscillation of a magnetic field. In suchembodiments, the material 104 is used to encapsulate the thermalablation implant and to form protrusions, as described above, to resistmigration and rotation of the implant.

To allow X-ray detection of the radioactive sources, the radioactivesources can include a radiopaque marker, which is typically made of adense, high atomic number material, such as gold or tungsten, which canblock the transmission of X-rays so that the radioactive source can bedetected by using X-ray imaging techniques. This can be accomplished,e.g., by including a ball, rod or wire constructed of a dense, highatomic number material, such as gold or tungsten, within the containerof a radioactive source (e.g., seed). Alternatively, the radioactiveseed (or other source) can be at least partially coated with aradiopaque material.

The therapeutic members of the present invention can be manufactured invarious manners. For example, a molding process, such as compressionmolding or injection molding can be used. In one example, a radioactivesource is placed into an embossing mold that includes the inverse (i.e.,negative) of the pattern of projections that is to be embossed on theouter surface of the polymeric material. Before or after the source(e.g., seed) is placed in the mold, a bio-absorbable polymer or someother plastic material is introduced into the mold at a temperature thatis above the melt point of the material such that the material flowsaround the seed within the mold cavity. The material is then allowed toset within the mold, e.g., by cooling the mold. After the material hasset, the mold is opened, and the finished therapeutic member with aplurality of polymeric projections is removed. In other embodiments, anencapsulating material is molded around the seed, and then theprotrusions are produced in a secondary process, e.g., by machining,crimping or otherwise altering the shape of the encapsulating materialto form protrusions. In still other embodiments, the protrusions areformed in the encapsulating material prior to the seed being placed intothe material. In still further embodiments, the protrusions can bedoughnut shaped pieces that are slid over the radioactive sourceimplant. These are just a few examples. Other techniques for producingthe protrusions are also within the scope of the present invention.

For the embodiment of FIGS. 7A and 7B, where the outer surface or themember 700 resembles a rough stucco surface, a mold can includepurposeful protrusions, or can simply be a rough surface that was formedwhen casting or otherwise manufacturing the mold. Typically, the metalof the mold would be machined such that a member produced using the moldwould have a generally smooth surface. However, in accordance with anembodiment of the present invention the mold is left rough, so that themember 700 formed using the mold would have random protrusions.

In another embodiment, a radioactive source 102 is encapsulated within apolymeric material, and then protrusions are attached to the outersurface of the encapsulating material in a secondary process. Forexample, while the outer surface of the encapsulating material is tacky,particles or strands can be attached to the outer surface to therebyform the protrusions. The outer surface of the encapsulating materialcan be made tacky by heating the material, coating the material with abio-compatible adhesive, or otherwise wetting the material. Theparticles or strands can then be attached to the outer surface of thematerial, e.g., by sprinkling the particles or strands onto the outersurface, or rolling the encapsulated source in the particle or strands.Such particles or strands should be bio-compatible, and can alsobio-absorbable. The particle or strands can be made of the same materialas the material 104 that encapsulates the radioactive source 102, butthis is not necessary. It is also possible that the container of theradioactive source be coated with a bio-compatible adhesive, and thatthe particles or strands are directly attached to the container of theradioactive source, to thereby form the protrusions that resistmigration and rotation.

In another embodiment, the material 104 can be molded or otherwiseformed around a source 102 such that a tab 808 extends longitudinally(i.e., axially) from each longitudinal end of the encapsulatedradioactive source 102, as shown in FIGS. 8A and 8B. In a secondaryprocess, each tab 808 is heated and formed into an anchor mechanism 810,shown in FIGS. 8C and 8D. More specifically, the main body of the member800 (within which the seed 102 is located) can be held in place whileeach tab 808 is melted into a desired shape by pushing against the tab808 with a heated surface or mold that is moved toward the main body ofthe member. The heated surface or mold that is used to melt the tab 808can simply be a flat surface, which will cause the anchor mechanism 810to have an amorphous shape. Alternatively, the mold that is used to meltthe tab 808 can be shaped to cause the anchor mechanism 810 to have aspecific shape, such as a square, as shown in FIGS. 8C and 8D. FIG. 8E,which is an end view of the member 800 shown in FIGS. 8C and 8D,includes exemplary dimensions in inches.

In FIGS. 8C-8E, the anchor mechanism 810 is square shaped. Inalternative embodiments the anchor mechanisms can have other shapes. Forexample, the anchor mechanism 810 can be amorphous, rectangular,triangular, trapezoidal, etc. In accordance with specific embodiments,an outer surface 812 of the anchor mechanism 810 is generallyperpendicular to the longitudinal axis 103 of the radioactive source102, as shown in FIGS. 8C and 8D. A void or groove 814 is formed betweenthe main portion of the member and the anchor mechanism 810, therebyallowing patient tissue to occupy this void 814 to reduce the tendencyfor the member 800, and the radioactive source 102 therein, to migrateor rotate.

It is preferred that the anchor mechanism 810 be located at eachlongitudinal end of the therapeutic member 800, as shown in FIGS. 8C and8D. However, in alternative embodiments the anchor mechanism 810 can belocated at only one of the longitudinal ends of the member. In FIGS.8A-8E the outer surface of the main body of the therapeutic member 800is shown as being generally cylindrical and smooth. However, this neednot be the case. The embodiments of FIGS. 1-7 discussed above can becombined with the embodiments of FIGS. 8A-8E. For example, a same moldthat is used to form the protrusions of FIGS. 1-7 can be used to formthe tabs 808, which can then shaped into the anchor mechanisms 810 in asecondary process after the members have been removed from the mold. Instill another embodiment, the anchor mechanisms 810 can be formed by anembossing mold similar to that used to form the protrusions of FIGS.1-7.

The radioactive sources 102 can be coated with or contain a drug and/orhormone. Alternatively, a drug and/or hormone can be included in theencapsulating material 104 that is used for form the protrusions oranchor mechanisms of the present invention.

Example types of materials 104 that are bio-absorbable include, but arenot limited to, synthetic polymers and copolymers of glycolide andlactide, polydioxanone and the like. Such polymeric materials are morefully described in U.S. Pat. Nos. 3,565,869, 3,636,956, 4,052,988 andEuropean Patent Publication No. 0030822, all of which are incorporatedherein by reference. Specific examples of bio-absorbable polymericmaterials that can be used to produce the therapeutic members ofembodiments of the present invention are polymers made by Ethicon, Inc.,of Somerville, N.J., under the trademarks “MONOCRYL” (polyglycoprone25), “MAXON” (Glycolide and Trimethylene Carbonate), “VICRYL”(polyglactin 910) and “PDS II” (polydioxanone).

Other exemplary bio-absorbable materials include poly(glycolic acid)(PGA) and poly(-L-lactic acid) (PLLA), polyester amides of glycolic orlactic acids such as polymers and copolymers of glycolate and lactate,polydioxanone and the like, or combinations thereof. Such materials aremore fully described in U.S. Pat. No. 5,460,592 which is herebyincorporated by reference. Further exemplary bio-absorbable polymers andpolymer compositions that can be used in this invention are described inthe following patents which are hereby incorporated by reference: U.S.Pat. No. 4,052,988 which discloses compositions comprising extruded andoriented filaments of polymers of p-dioxanone and 1,4-dioxepan-2-one;U.S. Pat. No. 3,839,297 which discloses compositions comprisingpoly[L(−)lactide-co-glycolide] suitable for use as absorbable sutures;U.S. Pat. No. 3,297,033, which discloses the use of compositionscomprising polyglycolide homopolymers as absorbable sutures; U.S. Pat.No. 2,668,162, which discloses compositions comprising high molecularweight polymers of glycolide with lactide; U.S. Pat. No. 2,703,316mwhich discloses compositions comprising polymers of lactide andcopolymers of lactide with glycolide; U.S. Pat. No. 2,758,987, whichdiscloses compositions comprising optically active homopolymers of L(−)lactide i.e. poly L-Lactide; U.S. Pat. No. 3,636,956, which disclosescompositions of copolymers of L(−) lactide and glycolide having utilityas absorbable sutures; U.S. Pat. No. 4,141,087, which disclosessynthetic absorbable crystalline isomorphic copolyoxylate polymersderived from mixtures of cyclic and linear diols; U.S. Pat. No.4,441,496, which discloses copolymers of p-dioxanone and2,5-morpholinediones; U.S. Pat. No. 4,452,973, which disclosespoly(glycolic acid)/poly(oxyalkylene) ABA triblock copolymers; U.S. Pat.No. 4,510,295, which discloses polyesters of substituted benzoic acid,dihydric alcohols, and glycolide and/or lactide; U.S. Pat. No.4,612,923, which discloses surgical devices fabricated from syntheticabsorbable polymer containing absorbable glass filler; U.S. Pat. No.4,646,741 which discloses a surgical fastener comprising a blend ofcopolymers of lactide, glycolide, and poly(p-dioxanone); U.S. Pat. No.4,741,337, which discloses a surgical fastener made from aglycolide-rich blend of polymers; U.S. Pat. No. 4,916,209, whichdiscloses bio-absorbable semi-crystalline depsipeptide polymers; U.S.Pat. No. 5,264,540, which discloses bio-absorbable aromaticpolyanhydride polymers; and U.S. Pat. No. 4,689,424, which disclosesradiation sterilizable absorbable polymers of dihydric alcohols. Ifdesired, to further increase the mechanical stiffness of the moldedembodiments of the present invention, bio-absorbable polymers andpolymer compositions can include bio-absorbable fillers, such as thosedescribed in U.S. Pat. No. 4,473,670 (which is incorporated byreference) which discloses a composition of a bio-absorbable polymer anda filler comprising a poly(succinimide); and U.S. Pat. No. 5,521,280(which is incorporated by reference) which discloses bio-absorbablepolymers and a filler of finely divided sodium chloride or potassiumchloride.

The final hardness of a polymer of the therapeutic members of thepresent invention should preferably be in a range from 20 to 80durometer and more preferably in the range of 20-40 durometer. However,members with other hardnesses are also within the scope of the presentinvention. Where the material 104 is bio-absorbable, the bio-absorbablematerial should preferably be absorbed in living tissue in a period oftime of from about 70 to about 120 days, but can be manufactured to beabsorbed anywhere in a range from 1 week to 1 year or more, depending onthe therapeutic plan for a specific patient. The material 104 shouldalso be bio-compatible, whether or not it is bio-absorbable. Thematerial 104 may also be bio-adhesive.

In accordance with an embodiment of the present invention, the minimumthickness of the material 104 that encapsulates the source 102 should beabout 0.002 inches. Such minimum thickness would occur at locationswhere there is not a protrusion. The preferred thickness of the material104 where there is not a protrusion is about 0.004 inches. As mentionedabove, the protrusions preferably extend at least 0.002 inches so thatthey can sufficiently grip into patient tissue. Such extension of theprotrusions is that which is beyond the underlying thickness of thematerial 104. The protrusions are preferably separated from one anothera sufficient distance such that the voids formed between the protrusionsallow patient tissue to occupy these voids to reduce the tendency forthe therapeutic member, and the radioactive source 102 therein, tomigrate or rotate. Preferably, these voids or spaces between protrusionsare at least 0.010 inches, so that patient tissue can fit into thesespaces. The overall dimensions of the therapeutic members of the presentinvention are limited by the inner diameter of the needle that is to beused to implant the members. For example, the larger the inner diameterof the needle, the more the protrusions can extend.

The term polymer, as used herein, is also meant to include copolymers.Table 2 below provides examples of bio-absorbable polymers suitable foruse in producing embodiments of the present invention, along withspecific characteristics (e.g., melting points) of the various polymers.A further discussion of such bio-absorbable polymers can be found in anarticle by John C. Middleton and Arthur J. Tipton entitled “SyntheticBiodegradable Polymers as Medical Devices,” published March 1998 inMedical Plastics and Bio-materials, which article is incorporated hereinby reference.

TABLE 2 Biodegradable polymers, properties and degradation time MELTINGGLASS- MOD- DEGRADA- POINT TRANSITION ULUS TION TIME POLYMER (° C.) TEMP(° C.) Gpa)^(a) (MONTHS)^(b) PGA 225-230 35-40 7.0  6 to 12 LPLA 173-17860-65 2.7 >24 DLPLA Amorphous 55-60 1.9 12 to 16 PCL 58-63 (−65)-(−60)0.4 >24 PDO N/A (−10)-0    1.5  6 to 12 PGA-TMC N/A N/A 2.4  6 to 1285/15 DLPLG Amorphous 50-55 2.0 5 to 6 75/25 DLPLG Amorphous 50-55 2.0 4to 5 65/35 DLPLG Amorphous 45-50 2.0 3 to 4 50/50 DLPLG Amorphous 45-502.0 1 to 2 ^(a)Tensile or flexural modulus. ^(b)Time to complete massloss. Rate also depends on part geometry.

FIG. 9 illustrates an exemplary applicator 900, often referred to as aMICK™ applicator, that can be used to implant the therapeutic members ofthe present invention at variable spaced locations within a patient'sbody. Such an applicator 900 is available from Mick Radio-NuclearInstruments, Inc., of Mount Vernon, N.Y.

The applicator 900 includes a hollow needle 912 insertable into thepatient's body, a needle chuck 913 for releasably holding the needle912, a magazine 914 for holding and dispensing therapeutic members ofthe present invention (containing seeds or other radioactive sources)into the needle chuck 913, a main barrel 916 connected to the needlechuck 913. Also shown in FIG. 9 is a stylet 917 extendable through themain barrel 916, the needle chuck 913, and a bore of the needle 912. Theapplicator 900 also includes a base frame member along which the needle912, the needle chuck 913, the magazine 914 and the main barrel 916 areslidably mounted. The frame member includes an abutment end 922 adaptedto abut a surface of the patient's body or a template (not shown) fixedwith respect to the body, a barrel collar 924 through which the mainbarrel 916 is slidable, and two rods 926 (only one can be seen in theside view of FIG. 9) extending between and fixedly attached to theabutment end 922 and the collar 924. The collar 924 is equipped with afinger ring 928 for receiving a finger of a user.

The applicator 900 is designed to allow the needle 912 to be moved indifferent increments with respect to the base frame. For this purpose,the main barrel 916 includes rows of detents or indentations 952 thatextend along the length of the barrel 916, with each row havingdifferent indentation spacing (only one row is shown in FIG. 9). Forexample, the applicator 900 can have a first row of indentations spacedat 3.75 mm, a second row of indentations spaced at 4.0 mm, a third rowof indentations spaced at 5.0 mm, a fourth row of indentations spaced at5.5 mm, and a fifth row of indentations at 6.0 mm. These spacings can bechanged as desired by using an applicator having a main barrel withother indentation spacings.

The barrel collar 924 includes a fixed portion 955 and a spacing dial956 rotatably mounted on the fixed portion 955. An operator can turn thedial 956 relative to the fixed portion 955 to select one of the rows orseries of indentations.

The magazine 914 includes a magazine head 933 and a cartridge 934 inwhich therapeutic members of the present invention can be stackedparallel to each other. A spring-loaded magazine plunger 938 is biasedagainst the therapeutic members (each of which includes a radioactivesource 102) at the upper end of the magazine 914 to facilitate movementof the therapeutic members into the needle chuck 913 and to provide anindication to the operator that a therapeutic member has been dispensedfrom the cartridge 934.

The cartridge 934 can be preloaded with a plurality of therapeuticmembers of the present invention (e.g., up to 20 members, each with aradioactive source 102) and then screwed into the magazine head 933. Thecartridge 934 can be keyed to the needle chuck 913 to prevent itsincorrect insertion into the needle chuck 913.

In the operation, the needle 912 is inserted into a patient in an areawhere a single radioactive source or row of radioactive sources is to beimplanted. Then, the needle chuck 913 of the body of the applicator 900is coupled with the protruding end of the needle 912 to prepare theapplicator 900 for use. An initial radioactive source spacing can be setby adjusting the spacing dial 956 to select a particular row ofindentations 952 on the main barrel 916 corresponding to the desiredspacing. The stylet 917, which is initially fully extended in the needle912, is then retracted from the needle 912 and the needle chuck 913,enabling a therapeutic member (including a radioactive source) from themagazine 914 to be positioned in the chuck 913 for movement into theneedle 912. When the style 917 is retracted, the therapeutic member ismoved into the chuck and the extended magazine plunger 938 will movefurther into the magazine 914, which will indicate to the operator thata member has been positioned for transfer into the needle 912. Thestylet 917 is then pushed through the barrel 916 against the therapeuticmember, forcing the member through the needle 912 and into the patient'sbody.

After a first member (including a radioactive source) has beenimplanted, the needle 912 is withdrawn from the patient's body by aparticular distance so that the next radioactive source to be implantedis spaced apart from the first radioactive source. Then, the stylet 917is again retracted to enable the next therapeutic member (with aradioactive source) from the magazine 914 to be positioned for movementinto the needle 912. The stylet 917 is then advanced through the needle912 to force the therapeutic member into the patient's body at a desireddistance away from the first member. This procedure is repeated forsubsequent therapeutic member implants. Additional details of thisprocess and the applicator 900 can be found in U.S. Pat. No. 5,860,909,which is incorporated herein by reference. This is just one example of adevice that can be used to implant therapeutic members of the presentinvention. Other devices may also be used, while still being within thescope of the present invention. For example, rather than usingcartridges as described above, therapeutic members of the presentinvention (and optionally, spacers therebetween) can be preloaded into aneedle that is used to implant a row of such members (and optionally,spacers therebetween) in a single needle track.

The conventional stylet 917 that is used with an applicator, such as aMick™ applicator, is made using a solid wire. However, this can resultin the mislocation of the sources in the needle track due to vacuumphenomena occurring as the needle and stylet are withdrawn. To overcomethis problem, the stylet 917 is preferably a vented stylet that includesa vent that extends the length of the stylet, as described in U.S. Pat.No. 6,554,760, which is incorporated herein by reference.

Embodiments of the present invention, as described above, are directedto therapeutic members that include protrusions and/or anchor mechanismsthat reduce the tendency for the therapeutic member and the radioactivesource therein to migrate and rotate within a patient's body afterimplantation. Embodiments of the present invention are also directed tocartridges, similar to 934, that are pre-loaded with such therapeuticmembers.

The above mentioned embodiments of the present invention relate totherapeutic members that include a single radioactive source (a singleseed, rod or coil). It is also possible that embodiments of the presentinvention can be used together with elongated members known as strandsthat include multiple radioactive sources that are spaced from oneanother, e.g., as described in U.S. patent application Ser. No.10/035,083, which was filed on Dec. 28, 2001, and which is incorporatedherein by reference. More specifically, one or more therapeutic memberas described in FIGS. 1-7, which each include a single radioactivesource 102, can be used together with one or more strand that includesmultiple radioactive sources.

For example, a single needle can be loaded with a therapeutic memberhaving a single radioactive source as well as with a strand havingmultiple radioactive sources, thereby allowing for implantation of bothduring the same procedure that include insertion and removal of theneedle. This would be useful, e.g., where a first radioactive source ina row of radioactive sources is to be located near a patient's bladderor urethra. If a strand of radioactive sources were being implanted, andthe end of the strand were inserted too far and into the patient causingit to enter the bladder or urethra, then the entire strand would have tobe removed from the patient. However, if the first radioactive sourceimplanted was within a therapeutic member of the present invention, andthat radioactive source got into the bladder or urethra, then it wouldbe possible to remove the single first radioactive source withoutremoving strand that followed the first radioactive source.

As mentioned above, seeds (or other radioactive sources) are sometimesimplanted into a patient by preloading a hollow needle with seeds andspacers that are used to maintain a desired distance between a row ofseeds, e.g., as described in U.S. Pat. No. 6,554,760, which isincorporated herein by reference. The seeds and spacers are deployedfrom the hollow needle using a stylet, which preferably includes aradial vent that extends the length of the stylet, to reduce themislocation of the radioactive sources in the needle track due to vacuumphenomena occurring as the needle and stylet are withdrawn. In suchimplants, the first and last seeds are the most likely seeds to migrateand/or rotate, however the other seeds, as well as the spacers, may alsomigrate and/or rotate within the needle track. To reduce migration ofthe seeds, therapeutic members of the present invention can be used.That is, a seed can be encapsulated by a material that includesprotrusions that will resist the migration and rotation of the seedtherein. In another embodiment, protrusions can be added to the spacersthat are used to maintain the desired distances between the radioactivesources. Such spacers with protrusions can be made in manners similar tothose explained above. For example, protrusions can be added topreexisting spacers (e.g., cylindrical spacers) by encapsulating thespacer with a material within which protrusions are formed.Alternatively, spacers can be manufactured to include protrusions. Suchspacers can be formed, e.g., using an embossing mold, or by machining,crimping or otherwise forming protrusions in an outer surface of thespacers. The spacers with protrusions can be used together withtherapeutic members having protrusions, or with radioactive sources thatdo not have protrusions. When used with radioactive sources not havingprotrusions, the spacers with protrusions would preferably be located atboth longitudinal ends of the radioactive sources, to thereby trap theradioactive sources in place. For example, if five radioactive seedswere to be implanted in a single needle track, six such spacers can beused (i.e., four spacers each of which separate pairs of seeds, and aspacer prior to the first seed, and a spacer following the last seed).The spacers that are located between seeds preferably includeprotrusions similar to those explained with reference to FIGS. 1-7. Thespacers that are located prior to the first seed and following the lastseed in the needle track can include protrusions similar to thoseexplained with reference to FIGS. 1-7, or can include anchor mechanismssimilar to those described above with reference to FIGS. 8A-8D. Thespacers with protrusions can be made entirely from a bio-absorbablematerial, examples of which are listed above. Alternatively, the spacerswith protrusions can be made from a non-bio-absorbable material which isbio-compatible. In still another embodiment, the spacer is made of abody that is bio-compatible but non-bio-absorbable, which isencapsulated within a bio-absorbable material that is used to form theprotrusions.

FIGS. 10A-10C illustrate a spacer 1000 according to another embodimentof the present invention. As shown in FIGS. 10A-10C, the spacer 1000includes two halves 1002 and 1004 that are connected by a living hinge1006. The halves 1002 and 1004 are shown as being half cylinders, butother shapes are also possible. The living hinge 1006 is biased suchthat after the spacer is folded into its closed position (FIG. 10B), thespacer tends to open up such that a gap 1008 forms between the twohalves (FIG. 10C). This can be accomplished, e.g., by molding the twohalves 1002 and 1004 and the living hinge 1006 in the open positionshown in FIG. 10A. The two haves 1002 and 1004 can then be folded towardone another along the living hinge 1006 to place the spacer 1000 in theclosed position shown in FIG. 10B, at which point the spacer can beinserted into a hollow needle used to implant spacers and radioactivesources in a patient. Once implanted in the patient, the spacer 1000will tend to open or unfold along the living hinge 1006, causing anouter surface of the spacer 1000 to thereby engage the patient tissuethat surrounds the spacer 1000. This engagement with patient tissue willcause the spacer to resist migration and rotation. To further resistmigration and rotation, protrusions, such as those discussed above, canbe added to the outer surface of the spacer. The spacer 1000 can be madeentirely from a bio-absorbable material, examples of which are listedabove. Alternatively, the spacer 1000 can be made from anon-bio-absorbable material which is bio-compatible.

In accordance with other embodiments of the present invention, an entirestrand 1100 that includes multiple radioactive sources (e.g., seeds)102, or portions of the strand 1100, can include the protrusions of thepresent invention, e.g., as shown in FIG. 11. Because a typical strandincludes polymeric material that attaches multiple radioactive sourcesto one another at desired spacings, a strand is not as susceptible tomigration and twisting as loose radioactive sources. Nevertheless, it isstill possible that that radioactive sources within the strands,especially the radioactive sources located near the distal ends of thestrand, can migrate and/or twist. By including protrusions that extendfrom the strand, the tendency for the strand or portions of the strandto migrate and/or twist can be reduced. Such protrusions can extend fromportions of the strand where radioactive sources are located, but canalternatively or additionally extend from other portions of the strand,such as the portions of the strand between the radioactive sources.

In another embodiment of the present invention, the anchor mechanism(e.g., 810) disclosed above with reference to FIGS. 8A-8E can be locatedat one or both longitudinal distal ends of a strand 1200 that includesmultiple radioactive sources 102, e.g., as shown in FIG. 12.

The strands 1100 and 1200 can be manufactured using similar moldingprocesses that were used to produce the therapeutic members of thepresent invention. For example, to produce the strand 1100, radioactivesources 102 can be placed into an embossing mold that allows theradioactive sources 102 to be spaced at the appropriate intervals in acavity of the embossing mold that is shaped to the desired finaldimensions, including the protrusions, of the strand. All the spacingsbetween the radioactive sources 102 can be of different lengths, if thepreoperative therapeutic plan so specifies. Spacers (not shown) can beplaced between radioactive sources 102 to keep a desired spacing betweenthe radioactive sources, if desired. Alternative means for maintainingthe spacings between adjacent radioactive sources may be used, as isknown in the art. The strand 1200 can be manufactured in a similarfashion as was just described, and as was described above with referenceto FIGS. 8A-8E.

In accordance with specific embodiments of the present invention, aresulting strand (e.g., 1100 or 1200) is a single solid monofilament ofa polymer with the radioactive sources 102 spaced within themonofilament and encapsulated at the appropriate intervals. The strandis preferably axially flexible. However, the strand preferably hassufficient column strength along its longitudinal axis so that thestrand can be urged out of a hollow needle without the strand foldingupon itself. Again, the intervals can be selected to be any distance orcombination of distances that are optimal for the treatment plan of thepatient.

In another embodiment, a strand can be made by inserting (i.e., pushing)radioactive sources and spacers through an opening in one end of anelongated hollow tube of bio-absorbable material. Additional details ofa seed pusher that can be used in this process are described in U.S.Pat. No. 6,761,680, which was incorporated herein by reference above.The protrusions of the present invention can be formed on the outersurface of the hollow tube prior to or after the insertion of theradioactive sources and spacers.

In a further embodiment, a strand can be constructed using a pair ofpre-formed elongated members of bio-absorbable material that are shapedlike half-shells, as described in U.S. Pat. No. 6,761,680, which isincorporated herein by reference. The two half-shells can be separatefrom one another. Alternatively, the two half shells can be connected bya living hinge along their length. The radioactive sources and spacersare placed within a first one of half-shells. The second half-shell isthen mated with the first half-shell, and the half-shells are fusedtogether (e.g., using ultrasonic welding or heat), thereby fixing theradioactive sources and spacers inside. The protrusions of the presentinvention can be formed on the outer surface of such half-shells beforeor after the radioactive sources and spacers are placed therein.

In still another embodiment, a strand can be made by inserting the seedsand spacers into a tube of braded bio-absorbable material. Additionaldetails of such a braded bio-absorbable tube are described in U.S. Pat.No. 5,460,592, which is incorporated herein by reference. Protrusionscan then be added, e.g., by slipping doughnut shaped rings over thebreaded material. Such doughnut shaped rings can also be slipped overany other type of strand that has a generally cylindrical outer surface.

In another embodiment, one or more spacers 1000 that are biased to open(as described above with reference to FIG. 10) can be incorporated intoa strand 1300, as shown in FIG. 13. The spacers 1000 can be incorporatedinto the strand 1300 in various manners, such as by insert molding theminto the strand. When the strand 1300 including such spacers 1000 isinserted into a hollow needle, the spacers 1000 will be kept in theirclosed position by the inner wall of the needle. However, once implantedin a patient, the spacers 1000 will at least partially open and engagethe tissue surrounding the spacer, thereby anchoring the entire strand1300. More generally, portions of the strand 1300 can be biased suchthat they at least partially open or expand to engage tissue surroundingthe strand. As shown in FIG. 13, the portions of the strand that open toengage surrounding tissue can be at one or both distal ends of thestrand and/or at locations between the distal ends. In FIG. 13, theliving hinges 1006 are shown as being along the length of the strand1300. However, this need not be the case. For example, a living hingecan be located at one or both of the longitudinal ends of the strand,and thus be perpendicular to the length of the strand.

Embodiments of the present invention are also directed to radiopaquemarkers that include protrusions and/or anchor mechanisms, similar tothose described above, to reduce the tendency of the markers to migrateand rotate within a patient's body after implantation. Such markers canbe made entirely or partially of a radiopaque material. Such aradiopaque material is often a dense, high atomic number material, suchas gold or tungsten, which can block the transmission of X-rays or otherradiation so that the markers can be detected using X-ray or otherradiation imaging techniques. For example, a marker can be a ball, rodor wire constructed from gold or tungsten. Alternatively, the marker canbe a container that includes a ball, rod or wire of radiopaque material,or a container at least partially coated with a radiopaque material. Onecommercially available marker is marketed under the trademark VISICOILand is available from RadioMed Corporation of Tyngsboro, Mass. These arejust a few examples of such markers. One of ordinary skill in the artwill understand that other markers are also possible. To add theprotrusions and/or anchor mechanisms to an existing marker, the markercan be encapsulated in a polymeric material within which protrusionsand/or anchor mechanisms are formed, in any of the manners describedabove. Alternatively, a marker can be manufactured to includeprotrusions and/or anchor mechanisms.

The markers can be implanted within a patient that will be undergoingexternal beam radiation therapy. If the patient is to also undergobrachytherapy, then the markers can implanted at the same time thatradiation sources are being implanted into the patient. In specificembodiments, radiopaque markers can be included in spacers and/orstrands of the present invention. By including a marker within a spaceror strand that includes protrusions and/or anchor mechanisms, the markertherein will also be resistant to migration and rotation.

In another embodiment, shown in FIGS. 14A-14D, an anchor mechanism 1400includes a sleeve 1404 to which are attached, by living hinges 1406,wings 1408. The wings 1408 are shown as being generally rectangular, butcan have other shapes. Two wings 1408 are shown, but more are less canbe used. The sleeve 1404 is intended to be placed around an underlyingstructure 1402, which can be a radioactive source (e.g., seed, rod orcoil), a thermal ablation implant, a spacer, a strand, or a radiopaquemarker. Each living hinge 1406 is biased in its open position (FIGS. 14Aand 14B), such that after the wings 1408 are folded into their closedpositions (FIGS. 14C and 14D), the wings 1408 will tend to open. Thiscan be accomplished, e.g., by molding the anchor mechanism 1400 in theopen position shown in FIGS. 14A and 14B. After being placed around anunderlying structure 1402, the wings 1408 can then be folded inwardalong the living hinges 1406 to be in the closed position shown in FIGS.14C and 14D. When in the closed position, the entire structure,including the underlying structure 1402 and anchor mechanism 1400, canbe inserted into a hollow needle used to implant the structure in apatient. The inner wall of the hollow needle will keep the wings 1408 intheir closed position. Because of the biasing of the living hinges 1406,once implanted in the patient, the wings 1408 will tend to open orunfold along the living hinges 1406, causing the wings 1408 to therebyengage the surrounding patient tissue. This engagement will resistmigration and rotation of the structure 1402. To further resistmigration and rotation, protrusions, such as those discussed above, canbe added to the wings 1408 and/or sleeve 1404. The anchor mechanism 1400can be made entirely from a bio-absorbable material, examples of whichare listed above. Alternatively, the anchor mechanism can be made from anon-bio-absorbable material which is bio-compatible.

The previous description of the preferred embodiments is provided toenable any person skilled in the art to make or use the embodiments ofthe present invention. While the invention has been particularly shownand described with reference to preferred embodiments thereof, it willbe understood by those skilled in the art that various changes in formand details may be made therein without departing from the spirit andscope of the invention.

1. A therapeutic implant configured and adapted to be implanted at leastone of between radioactive seeds and in a similar manner as looseradioactive seeds are implanted, for use in brachytherapy, comprising: apolymeric body; wherein an outer surface of the polymeric body definesone or more ribs having a substantially squared profile formed by astepped portion extending between a pair of sidewalls to reduce atendency of the implant to migrate and rotate within a patient's bodyafter implantation; and wherein a thickness of the polymeric body variessuch that the thickness is greater where there is one of said one ormore ribs than where there is not a rib.
 2. The therapeutic implant ofclaim 1, wherein the polymeric body is bio-absorbable.
 3. Thetherapeutic implant of claim 1, wherein the implant is molded.
 4. Thetherapeutic implant of claim 1, wherein the one or more ribs are definedby a shape of a mold.
 5. The therapeutic implant of claim 1, wherein theone or more ribs form one or more rings or a helix about the radialcircumference of the other surface of the polymeric body.
 6. Thetherapeutic implant of claim 1, wherein the polymeric body includesfirst and second longitudinal rounded ends, and wherein the one or moreribs are located between the longitudinal ends of the polymeric body. 7.The therapeutic implant of claim 1, wherein the polymeric body isbio-adhesive.
 8. The therapeutic implant of claim 1, wherein thepolymeric body is bio-adherent.
 9. The implant of claim 1, wherein adrug is at least one of coated onto said polymeric body and included inpolymeric material of the polymeric body.
 10. The implant of claim 1,wherein said implant is a spacer and is adapted to be positioned betweenother implants.
 11. A therapeutic implant configured and adapted to beimplanted at least one of between radioactive seeds and in a similarmanner as loose radioactive seeds are implanted, for use inbrachytherapy, comprising: a polymeric body; wherein an outer surface ofthe polymeric body includes a plurality of ribs, each of said ribshaving a substantially squared profile formed by a stepped portionextending between a pair of sidewalls to reduce a tendency of theimplant to migrate and rotate within a patient's body afterimplantation; and wherein the ribs are defined by variations in athickness of the polymeric body.
 12. The therapeutic implant of claim11, wherein the polymeric body is bio-absorbable.
 13. The therapeuticimplant of claim 11, wherein the polymeric body is bio-adhesive.
 14. Thetherapeutic implant of claim 11, wherein the polymeric body isbio-adherent.
 15. The implant of claim 11, wherein a drug is at leastone of coated onto said polymeric body and included in polymericmaterial of the polymeric body.
 16. The implant of claim 11, whereinsaid implant is molded.
 17. A therapeutic implant configured and adaptedto be implanted in a patient at least one of between radioactive seedsand in a similar manner as loose radioactive sees are implanted,comprising: a polymeric body with a longitudinal axis, said polymericbody being cylindrical, and first and second polymeric rounded end ribsextending from said polymeric body; said first polymeric rounded end ribincluding a first inwardly facing sidewall which is substantiallyperpendicular to the longitudinal axis; said second polymeric roundedend rib including a second inwardly facing sidewall which issubstantially perpendicular to the longitudinal axis, with the firstinwardly facing sidewall facing said second inwardly facing sidewall;said polymeric body including a first polymeric rib and a secondpolymeric rib, said first and second polymeric ribs completelyencircling said polymeric body and with said first and second ribslocated between the first inwardly facing sidewall and the secondinwardly facing sidewall, with said first polymeric rib spaced from saidfirst polymeric rounded end rib, and said second polymeric rib spacedfrom said first polymeric rib, and said second polymeric rounded end ribspaced from said second polymeric rib; said first polymeric ribincluding third and fourth sidewalls that are substantiallyperpendicular to said longitudinal axis; said second polymeric ribincluding fifth and sixth sidewalls that are substantially perpendicularto said longitudinal axis; wherein said therapeutic implant is adaptedto be urged out of a needle to be implanted in a patient and whereinsaid therapeutic implant is adapted to receive tissue between the firstinwardly facing sidewall and said third sidewall, between said fourthsidewall and said fifth sidewall, and between said sixth sidewall andsaid second inwardly facing sidewall, when the therapeutic implant isimplanted in a patient in order to reduce the tendency of thetherapeutic implant to migrate within the patient's body.
 18. Theimplant of claim 17, wherein a drug is at least one of coated onto saidpolymeric body and included in polymeric material of the polymeric body.19. The implant of claim 17, wherein said implant is a spacer and isadapted to be positioned between other implants.
 20. A therapeuticimplant configured and adapted to be implanted in a patient at least oneof between radioactive seeds and in a similar manner as looseradioactive seeds are implanted comprising: a cylindrical polymeric bodywith a longitudinal axis, first and second polymeric rounded end ribsextending from said polymeric body; said first polymeric rounded end ribincluding a first inwardly facing sidewall which is substantiallyperpendicular to the longitudinal axis; said second polymeric roundedend rib including second inwardly facing sidewall which is substantiallyperpendicular to the longitudinal axis with the first inwardly facingsidewall facing said second inwardly facing sidewall; a first polymericrib, said first polymeric rib completely encircling the polymer body,said first polymeric rib located between the first inwardly facingsidewall and the second inwardly facing sidewall, with said firstpolymeric rounded end rib spaced from said first polymeric rib and saidfirst polymeric rib spaced from said second polymeric rounded end rib;said first polymeric rib including third and fourth sidewalls that aresubstantially perpendicular to said longitudinal axis; and wherein saidtherapeutic implant is adapted to be urged out of a needle to beimplanted in a patient and wherein said therapeutic implant is adaptedto receive tissue between the first inwardly facing sidewall and saidthird sidewall and between said fourth sidewall and said second inwardlyfacing sidewall when the therapeutic implant is implanted in a patientin order to reduce the tendency of the therapeutic implant to migratewithin the patient's body.
 21. The implant of claim 20, wherein a drugis at least one of coated onto said polymeric body and included inpolymeric material of the polymeric body.
 22. The implant of claim 20,wherein said implant is a spacer and is adapted to be positioned betweenother implants.
 23. A therapeutic implant configured and adapted to beimplanted in a patient at least one of between radioactive seeds and ina similar manner as loose radioactive seeds are implanted, for use inbrachytherapy, comprising: a longitudinal axis; a polymeric body withopposite ends; a pair of ribs, the ribs capping opposite respective endsof the polymeric body; wherein each of the ribs from the pair of ribsincludes a sidewall substantially perpendicular to the longitudinalaxis; and at least one additional rib encircling the polymeric body, theat least one additional rib arranged between the pair of ribs cappingthe opposite ends of the polymeric body; wherein the at least oneadditional rib includes a surface, connected between a pair ofadditional sidewalls, the additional sidewalls being substantiallyperpendicular to the longitudinal axis and substantially perpendicularto the surface of the at least one additional rib; and wherein thetherapeutic implant is adapted to receive tissue between the additionalsidewalls of the at least one additional rib and sidewalls of the pairof ribs capping opposite ends of the polymeric body when the therapeuticimplant is implanted in a patient's body to reduce a tendency of theimplant to migrate within the patient's body after implantation.
 24. Theimplant of claim 23, wherein a drug is at least one of coated onto saidpolymeric body and included in polymeric material of the polymeric body.25. The implant of claim 23, wherein said implant is a spacer and isadapted to be positioned between other implants.
 26. A therapeuticimplant configured and adapted to be implanted in a patient at least oneof between radioactive seeds and in a similar manner as looseradioactive seeds are implanted, for use in brachytherapy, comprising: apolymeric body with rounded opposite ends with a longitudinal axis; apair of ribs extending from the polymeric body, the ribs capping theopposite respective ends of the polymeric body so that the ribs guidethe therapeutic implant when positioned within and urged through aneedle; wherein each of the ribs from the pair of ribs includes asidewall substantially perpendicular to the longitudinal axis; and atleast one additional rib defined by the outer surface of the polymericbody encircling the polymeric body, the at least one additional ribarranged between the pair of ribs capping opposite ends of the polymericbody; wherein the at least one additional rib includes a surfaceconnected between a pair of additional sidewalls, the additionalsidewalls being substantially perpendicular to the longitudinal axis ofthe polymeric body and substantially perpendicular to the surface of theat least one additional rib; wherein the therapeutic implant is adaptedto receive tissue between the additional sidewalls of the at least oneadditional rib and the sidewalls of the pair of ribs capping oppositeends of the polymeric body when the therapeutic implant is implanted ina patient's body to reduce a tendency of the therapeutic implant tomigrate within the patient's body after implantation; and wherein thepair of ribs and the at least one additional rib are defined byvariations in a thickness of the polymeric body.
 27. The implant ofclaim 26, wherein a drug is at least one of coated onto said polymericbody and included in polymeric material of the polymeric body.
 28. Theimplant of claim 26, wherein said implant is a spacer and is adapted tobe positioned between other implants.
 29. A therapeutic implantconfigured and adapted to be implanted in a patient at least one ofbetween radioactive seeds and in a similar manner as loose radioactiveseeds are implanted, for use in brachytherapy, comprising: a polymericbody with a longitudinal axis and with rounded opposite ends; a pair ofribs extending from the polymeric body, the ribs capping opposite endsof the polymeric body; wherein each of the ribs from the pair of ribsincludes a sidewall substantially perpendicular to the longitudinalaxis; and at least one additional rib extending from the polymeric bodyand encircling the polymeric body, the at least one additional ribarranged between the pair of ribs capping opposite ends of the polymericbody; wherein the at least one additional rib includes a pair ofadditional sidewalls substantially perpendicular to the longitudinalaxis; and wherein the therapeutic implant is adapted to receive tissuebetween the additional sidewalls of the at least one additional rib andthe sidewalls of the pair of ribs capping opposite ends of the polymericbody when the therapeutic implant is implanted in a patient's body toreduce a tendency of the implant to migrate within the patient's bodyafter implantation.
 30. The implant of claim 29, wherein a drug is atleast one of coated onto said polymeric body and included in polymericmaterial of the polymeric body.
 31. The implant of claim 29, whereinsaid implant is a spacer and is adapted to be positioned between otherimplants.